docs: def add_doc_to_update(self, action, update_spec, action_buffer_index):
          """
          Prepare document for update based on Elasticsearch response.
          Set flag if document needs to be retrieved from Elasticsearch
          """
  
          doc = {
              "_index": action["_index"],
              "_type": action["_type"],
              "_id": action["_id"],
          }
  
          # If get_from_ES == True -> get document's source from Elasticsearch
          get_from_ES = self.should_get_id(action)
          self.doc_to_update.append((doc, update_spec, action_buffer_index, get_from_ES))